Comparison of the in situ compressive behavior of carbon fibers woven ply laminates exposed to one‐sided heat flux: Thermoplastic versus thermosetting composites

Abstract

AbstractThis study investigates the influence of a combined thermal heat flux (imposed by a cone calorimeter) and a compressive loading on the deformation and damage mechanisms within quasi‐isotropic carbon fibers reinforced thermoplastic (polyetherether ketone [PEEK] and polyphenylene sulfide [PPS]) and thermosetting (epoxy) laminates. First, thermogravimetric Analyses conducted under nitrogen provide valuable information on the thermal decomposition of these materials depending on the matrix nature (580–510°C and 350°C, respectively) which is a key factor to explain the mechanical behavior under fire conditions. Second, under the same testing conditions (creep loading under a 50 kW/m2 heat flux), the time to failure is about 17 times as high (C/PEEK), twice as high (C/PPS) with respect to C/epoxy laminates. At the ply scale, the exposure of thermoplastic matrices (PEEK and PPS) to a 50 kW/m2 heat flux causes softening and thermal decomposition, facilitating the micro‐buckling of fiber bundles in matrix‐rich areas. At the laminates scale, this mechanism ultimately leads to the formation and propagation of plastic kink bands in the transverse direction. In epoxy‐based laminates, the onset of matrix pyrolysis occurs at lower temperatures (350°C) during thermal aggression, and thermal decomposition has started in all the plies of the laminates. Combined with the low ductility of the epoxy matrix, the compressive response is elastic‐brittle and results from the buckling of 0° plies outside the thermally‐damaged area.Highlights Study on the compression of polymer composites exposed to a 50 kW/m2 heat flux. The influence of the matrix nature (thermoplastic vs thermoset) is discussed. Time to failure is about 17 times higher in C/PEEK compared to C/Epoxy. Plastic kink bands propagate in thermoplastic composites at T > Tg. C/Epoxy laminates undergo buckling outside the thermally damaged area.